<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        ul {
            list-style: none;
            border: 1px solid #dddddd;
            width: 180px;

        }

        li {
            padding: 5px;
        }
    </style>
</head>

<body>
    <div id="app">
        <ul>
            <li>返回</li>
            <li>重新加载</li>
            <li>另存为（A）</li>
            <li>打印（P）</li>
            <li>查看网页源代码</li>
        </ul>
    </div>
</body>
<script>
    let ul = document.querySelector('#app>ul')
    console.log(ul);
    document.oncontextmenu = function (e) {
       
    }
</script>

</html>